1. Field of the Invention
The present invention relates to a substrate processing apparatus including a processing unit for performing predetermined processing for a substrate such as a semiconductor wafer, an LCD substrate (a glass substrate for a liquid crystal display) or the like and a substrate carrier apparatus for transferring the substrate to/from the processing unit, and a method of aligning a substrate carrier apparatus for aligning the substrate carrier apparatus with respect to the processing unit.
2. Description of the Related Art
In manufacturing processes of a semiconductor device, the photolithography technique is used in which a resist solution is applied to a substrate such as a semiconductor wafer (hereinafter, referred to as a wafer), and a resultant resist film is exposed to light using a photomask and developed, thereby creating a desired resist pattern on the substrate. Such processing is generally performed using a substrate processing apparatus constituted of a coating and developing apparatus for applying and developing a resist solution and an aligner connected thereto.
To reduce the area occupied by the apparatus while ensuring a high throughput, the aforementioned substrate processing apparatus has the required number of units for each processing, the unit being a processing apparatus unitized to perform each of different plural processing such as coating treatment, developing treatment, heating and cooling processing, and so on for a substrate, and further has a carrier apparatus for carrying the substrate into/out of each unit.
The substrate processing apparatus described above will be briefly described taking, for example, a coating and developing apparatus shown in FIG. 14 as an example. A carrier 10 housing, for example, 25 wafers W is carried into a carrier stage 11, and the wafers W are taken out by a transfer arm 12 and carried to a processing block 14 via a transfer unit of a shelf unit 13a. In the processing block 14, a carrier apparatus 15 is provided at the center, around which a coating unit 16a for applying a coating solution to the wafer W, a developing unit 16b for performing developing treatment for a wafer after exposure, and shelf units 13a, 13b, and 13c including a heating unit and a cooling unit for performing predetermined heating processing and cooling processing for the wafer W before and after the treatments in the coating unit 16a and the developing unit 16b are provided.
The carrier apparatus 15 is for transferring the wafer W to/from the coating unit 16a, the developing unit 16b, and each of the processing units provided in the shelf units 13a to 13c in the processing block 14, and configured to be ascendable and descendable, rotatable about the vertical axis and movable back and forth.
Each unit such as the coating unit 16a, the developing unit 16b, or the like is housed, for example, in a container 17 as shown in FIG. 15, and the wafer W is transferred to/from a mounting table (not shown) for a wafer W provided inside the container 17 through a carrier opening 18 formed in a face of the container 17 opposed to the carrier apparatus 15.
Incidentally, in the above-described apparatus, it is required to mount the wafer W with high accuracy within a predetermined mounting region of each processing unit by the carrier apparatus 15 through the carrier opening 18 in order to perform accurate processing for the wafer W in each processing unit. To prevent particles from entering from a carrier path in this event, the carrier opening 18 is formed in the smallest possible size for an arm of the carrier apparatus 15 holding the wafer W to be able to enter and exit. Therefore, the carrier apparatus 15 cannot smoothly enter the inside of the processing unit such that the wafer W and the carrier apparatus 15 tend to collide with a region in the vicinity of the carrier opening 18. Therefore, to prevent the collision, an operation is performed at the time of initial setting of a system such as confirming the position of the carrier opening 18 of each processing unit in advance and causing the carrier apparatus 15 to learn, for example, an entrance/exit position of its arm with respect to the carrier opening 18 when carrying the wafer W into/out of the processing unit. This operation is generally called teaching and performed by manual operation of an operator.
It is very troublesome and takes much time, however, to perform the teaching operation of the carrier apparatus 15 for the carrier openings 18 of all the processing units by manual operation of the operator, and therefore the present inventor considers a configuration of automatically detecting the carrier opening 18 of a processing unit and aligning the carrier opening 18 with the carrier apparatus 15. As the configuration of automatically aligning the carrier apparatus 15 with the processing unit in the above-described manner, there is a proposed configuration disclosed in Japanese Patent Application Laid-open No. 2001-117064.
In this configuration, as shown in FIG. 16, alignment marks 110 are placed on front faces of processing units 100 with the positional relation with respect to actual transfer positions of the processing units 100 being grasped in advance, while a CCD camera 130 placed on a carrier apparatus 120 reads the alignment mark 110 in a predetermined positional relation, so that based on the detected data the position of the carrier apparatus 120 when transferring a substrate to the processing unit 100 is calculated, and based on the calculated positional data the entrance position of the substrate of the carrier apparatus 120 into the processing unit 100 and the transfer position of the substrate are corrected.
In the configuration disclosed in the aforementioned document, the carrier apparatus 120 can detect the position of the alignment mark 110 since it is configured to be movable in the vertical direction (a z-direction) of a carrier opening 140 of the processing unit 100 and movable in the lateral direction (a y-direction) of the carrier opening 140 and employs a CCD camera 130. However, in consideration of the type of carrier apparatus which moves to rotate about the vertical axis such as the carrier apparatus 15 of the above-described substrate processing apparatus in place of the carrier apparatus 120, this type of carrier apparatus cannot move along the lateral direction of the carrier opening 140. Accordingly, it is possible to precisely grasp the positional relation in the vertical direction of the carrier opening 140 but hard to precisely grasp the positional relation in the lateral direction and difficult to perform accurate teaching. Further, there is another problem that the CCD camera 130 used as a detecting means of the alignment mark 110 is expensive.
Further, in the configuration of the aforementioned document, the entrance position into the processing unit 100 and the transfer position of the carrier apparatus 120 are corrected based on the alignment mark 110 of the processing unit 100, but it is difficult to mount the wafer on the spin chuck being a mounting section of, for example, the coating unit with the rotation center of the spin chuck being precisely aligned with the center of the wafer by this alignment method.
This is because although the rotation center of the spin chuck can be roughly aligned with the center of the wafer based on the aforementioned mark position by obtaining the relative positional relation between the center position of the spin chuck and the position of the alignment mark 110 for each processing unit 100 in advance, the center of the spin chuck and the center of the rotation axis do not always coincide with each other but may slightly differ from each other due to parts error and assembly error of the spin chuck itself.
In the coating unit, treatment called edge rinse for cleaning by supplying a cleaning solution from a cleaning solution nozzle to the edge of the wafer with the wafer being rotated about the vertical axis is performed after application of the coating solution onto the front face of the wafer. In this event, there may appear a portion where the edge is not cleaned and a portion where the edge is cleaned in a width equal to or greater than a predetermined width if the center of the wafer is displaced from the rotation center of the spin chuck. It is desired to keep a device region of a wafer as large as possible, for example, to bring a device region up to a position not more than 1 mm from the edge. For this purpose, it is necessary to align the wafer center with the rotation center of the spin chuck at an accuracy within, for example, several tens μm, but it is difficult to align the wafer center with the rotation center of the spin chuck at an accuracy within several tens μm in the configuration of the aforementioned document, failing to accept this desire.